Modern vehicle brake systems allow for slowing or stopping movement of the vehicle in a controlled manner. A typical automobile or light truck brake system includes a disc brake assembly for each of the front wheels and either a drum brake assembly or a disc brake assembly for each of the rear wheels. The brake assemblies are simultaneously actuated by hydraulic or pneumatic pressure generated when an operator of the vehicle depresses a brake pedal. The structures of these drum brake assemblies and disc brake assemblies, and their actuators, are well known in the art.
A typical disc brake assembly includes a rotor which is secured to the wheel of the vehicle for rotation therewith. The rotor has a pair of opposed friction faces which are selectively engaged by portions of a caliper assembly. The caliper assembly is slidably supported by pins secured to an anchor plate. This anchor plate is in turn secured to a non-rotatable component of the vehicle, such as the suspended wheel hub. A pair of brake pads (or shoes) are disposed in the caliper assembly on opposite sides of the rotor. These brake pads are operatively connected to one or more hydraulically actuated pistons for movement between a non-braking position, wherein they are spaced apart from the opposed friction plates of the rotor; and a braking position, wherein they are moved into frictional engagement with the opposed friction plates of the rotor. Depressing the brake pedal causes the piston to urge the brake pads from the non-braking position to the braking position, frictionally engaging the friction faces to the rotor and thereby slowing or stopping the rotation of the associated wheel of the vehicle.
Each brake pad is made up of a relatively thick, substantially planar metallic body (the backing plate) to which is attached a cake of friction material (typically a molded composite material) in various ways (including adhesive, rivets, and integral molding into holes or raised features in/on the backing plate).
Backing plates for brake pads are typically made of a single piece of solid steel. The backing plate distributes the force of the caliper piston across the brake pad, and thus it has been believed that a single piece solid backing plate is necessary to provide sufficient strength and rigidity. However, such pieces are very heavy, particularly in large truck applications. This has been a recognized problem in the art. Weight on the sprung or suspended components of a vehicle degrades ride quality and handling, as well as leading to increased fuel consumption and waste of valuable material. There have been attempts to address the weight issue by making a slightly thinner backing plate that is “thickened” in local areas (typically edge perimeter) by embossing. However, the resulting plates are still quite heavy.
It would be desirable to provide a lighter weight alternative, taking advantage of other materials' beneficial properties, while maintaining strength and rigidity.